The present invention relates to integrated circuits. More particularly, the invention relates to multiple-layer integrated circuits having a selective temperature coefficient of resistance.
The operation of integrated circuits (ICs) may be influenced by its operating temperature, and therefore, operating temperature ranges must be taken into account during the design and fabrication of integrated circuits. For example, one element of an integrated circuit that is affected by temperature is a resistor. A change in operating temperature often affects a change in current. The temperature dependence of a resistor adversely effects performance of the IC in certain ranges of operating temperature.
Temperature coefficient of resistance (TCR) refers to the change in resistance per change in temperature degree. Some materials have a positive TCR, meaning resistance increases as operating temperature increases, and some materials have a negative TCR, meaning resistance decreases as operating temperature increases. A material having a zero TCR does not exhibit changes in resistance due to changes in operating temperature.
The ability to select a given TCR by design of the integrated circuit may be desirable, but previously this has only been possible with integrated circuit processes that provide multiple types of resistors of varying TCR materials. Generally, the TCR of a thin-film resistor is controlled by the individual TCR of each constituent film, and there is a lack of additional tunability wherever the film compositions are fixed. Additionally, these currently used thin-filmed resistors are bulky and not generally compatible with very-large scale integration (VLSI) semiconductor technology.